The present invention relates to a method of hardening a clothing wire for processing textile fibres and to an apparatus system therefor, the clothing wire having a succession of teeth arranged in its longitudinal direction, and the clothing wire being guided through a heating region in a pass-through direction for contact with at least one open flame, the heating region being followed by a quenching bath having a quenching liquid and by a subsequent tempering apparatus.
Clothing wires have a sawtooth profile and are drawn onto cylindrical drums or rolls to form a carding machine. As a result, the carding machines have an envelope surface which is provided with teeth; a clothing wire can be used, for example, to form a cylinder or doffer and can have a length of several kilometers. In order to provide the clothing wire with sufficient strength and wear-resistance, methods of hardening the clothing wire, which are based especially on flame hardening, are known.
In the process, the hardening method preferably makes use of an open flame to form a heating region, through which the clothing wire is guided in its longitudinal direction. In the process, only the teeth are to be hardened and the tooth foot should have a high degree of toughness, which can be achieved, for example, by means of soft annealing.
Upstream of the heating region there can be provided a rinsing chamber, which allows at least partial cleaning of the clothing wire. After passing through the heating region, the clothing wire has to be quenched, for which purpose the clothing wire is led into a quenching bath filled with a quenching liquid. Following on therefrom, the clothing can be led through a tempering apparatus and through a cooling apparatus which follows on from the tempering apparatus.
Hardening a clothing wire over an open flame has been found to be especially advantageous, although scale can form on the surface of the clothing wire, which is always to be avoided. Especially when drawing the clothing wire onto a drum or roll, problems can arise when the clothing wire surface has scaling, because the clothing wire has to be drawn onto the cylindrical roll helically with a high degree of dimensional accuracy, and for drawing-on there is used a wire-guiding device, which cannot function properly in the case of a clothing wire surface that has scaling.
From DE 10 2005 025 627 B3 there is known a method of hardening a clothing wire, in which it is proposed that the hardening process itself be carried out with exclusion of oxygen. For that purpose protective gas has to be introduced into the heating region, with only so much oxygen being added for formation of the open flame as is necessary for reaction with a fuel gas. In order to feed in a protective gas whilst simultaneously introducing a fuel/air mixture, there is proposed a mixing device so that the fuel/air mixture is burnt in such a way that no non-combusted oxygen reaches the clothing wire. Accordingly the atmosphere in the heating region has to be kept free of oxygen, for which purpose therefore the protective gas is additionally introduced into the heating region.
However, further tests have shown, surprisingly, that scaling on the clothing wire at the exit from the heating region can be avoided even without introducing protective gas into the heating region. The reason therefor may be residues of cleaning agents, oils or other hydrocarbons which adhere to the surface of the clothing wire and which burn in the open flame and so prevent a reaction of the clothing wire with oxygen. The finding is based especially on the fact that at the immediate exit of the clothing wire from the heating region there is no scaling on the surface of the clothing wire. However, after following through the complete method for hardening the clothing wire, scaling is nevertheless to be found on the surface of the clothing wire. From this scale formation it can be concluded that the clothing wire, whilst still in a hot state, comes into contact with a reactant, which is to be avoided.